1. Field
The present invention relates to a heat radiation substrate and a method of manufacturing the same, and more particularly, to a method of efficiently manufacturing a heat radiation substrate having improved heat radiation characteristics and warpage characteristics by fabricating a high-strength metal core having through-holes preformed therein without additionally performing a hole formation process using a metal injection molding (MIM) process and then applying the metal core to a metal core substrate, and to a heat radiation substrate manufactured using the method.
2. Description of the Related Art
In a set of a mobile phone, a server, a network etc., which is speeding up, consumes high power, is highly integrated, and is decreased in size, the efficient heat-radiation of the set is a very important factor that serves to improve the reliability of the product and to prevent the malfunctions thereof. The principal cause of errors of the set, such as malfunctions, stoppage, and the like, is a chip having a high exothermic temperature.
In order to decrease the temperature of the chip, technologies of forcibly discharging a high heat generated from a chip by providing a radiation fin on the chip and driving a cooling fan have been used to date.
The radiation of a package is largely conducted through an air-cooling method using a radiation fin and a cooling fan and a water cooling method using a refrigerant or water. However, these air cooling and water cooling methods are problematic in that large-sized cooling apparatuses are required, and vibration and noise are generated.
In particular, as products are highly functionalized, the size of a cooling fan must be increased in order to improve the radiation performance thereof. Therefore, additional radiation measures are required because the cooling fan has a limited inner space and has a noise problem due to the high speed thereof.
Recently, novel cooling systems which can overcome vibration and noise have been developed. However, there is a problem in that they are expensive. Therefore, package industries are increasingly interested in the solution of heat radiation problems using a substrate. Since a substrate, which has a multi-layered structure, is composed of polymer resin having a very low thermal conductivity of 0.01 W/mK or less, the flow of heat generated in a chip is very poor.
In a general package, as the substrate structure shown in FIG. 6A, the path through which heat is rapidly transferred from a chip to a substrate is a path in which bump joints are connected to solder joints connected with a main board through a circuit layer made of Cu. However, the heat flowing through the path encounters great resistance due to an insulation layer having low thermal conductivity. Therefore, in order to enhance the heat radiation characteristics of a substrate, as a thermal via formed substrate and a metal core inserted substrate shown in FIGS. 6B and 6C, products that can decrease the temperature of a chip using a thermal via for radiation, which is made of Cu, formed at a portion of the substrate that is coupled with a chip, or a metal core inserted into the substrate, have come into the market.
These substrates with enhanced heat radiation characteristics have better heat radiation characteristics than those of the substrate shown in FIG. 6A, but have limitations in solving the radiation problem of a package that meets a high specification.
Hereinafter, a conventional method of manufacturing a heat radiation substrate having a metal core will be described with reference to FIG. 7A to 7H.
First, a dry film 12 is applied on both surfaces of a metal core 11, such as aluminum, holes 13 having a diameter of about 0.5 mm are formed in the metal core 11 through general exposure, developing and etching processes, and then the dry film is removed from the metal core 11 (see FIG. 7A to 7D).
Subsequently, an insulating resin 14, such as a prepreg, is applied on the both surfaces of the metal core 11 and in the holes 13, and then through-holes 15, having a diameter of about 0.25˜0.3 mm, are formed through a CNC drilling process (see FIGS. 7E and 7F).
Subsequently, a copper seed layer 16 is formed through an electroless copper plating process, and then a circuit pattern 17 for a core including a via 18 is formed through a circuit forming process including an electrolytic plating process and a plugging process (see FIGS. 7G and 7H).
However, in the conventional method of manufacturing a heat radiation substrate having a metal core, there is a problem in that the sizes of the holes are not uniform due to the excess etching of the metal core at the time of forming holes through an etching process. Further, when a high-strength material, such as a carbon nanotube, is used as a material of the metal core, there is a problem in that it is difficult to form holes, and thus the material of the metal core is limited.